Department of Biology, Georgia State University, Atlanta, GA, USA.
Autophagy. 2023 Feb;19(2):720-723. doi: 10.1080/15548627.2022.2094606. Epub 2022 Jul 7.
SQSTM1/p62 (sequestosome 1) is a well-established indicator of macroautophagic/autophagic flux. It was initially characterized as the ubiquitin-binding autophagic receptor in aggrephagy, the selective autophagy of ubiquitinated protein aggregates. Recently, several studies correlated its levels with the abundance of intracellular lipid droplets (LDs). In the absence of a bona fide receptor for the selective autophagy of LDs (lipophagy), a few studies demonstrated the role of SQSTM1 in lipophagy. Our analysis of these studies shows that SQSTM1 colocalizes with LDs, bridges them with phagophores, is co-degraded with them in the lysosomes, and affects LD abundance in a variety of cells and under diverse experimental conditions. Although only one study reported all these functions together, the overwhelming and complementary evidence from other studies suggests that the role of SQSTM1 in lipophagy via tagging, movement, aggregation/clustering and sequestration of LDs is rather a common phenomenon in mammalian cells. As ubiquitination of the LD-associated proteins under stress conditions is increasingly recognized as another common phenomenon, some other ubiquitin-binding autophagic receptors, such as NBR1 and OPTN, might soon join SQSTM1 on a list of the non-exclusive lipophagy receptors.: LD: lipid droplet; LIR: LC3-interacting region; PAT: Perilipin, ADRP and TIP47 domain; SAR: selective autophagy receptor.
SQSTM1/p62(自噬体相关蛋白 1)是一种成熟的巨自噬/自噬流的标志物。它最初被描述为聚泛素化蛋白聚集体选择性自噬(即巨自噬)的泛素结合自噬受体。最近,有几项研究将其水平与细胞内脂滴(LDs)的丰度相关联。由于缺乏 LD 选择性自噬(即脂噬)的真正受体,少数研究表明 SQSTM1 在脂噬中的作用。我们对这些研究的分析表明,SQSTM1 与 LDs 共定位,与吞噬体连接,与它们一起在溶酶体中降解,并在多种细胞和不同的实验条件下影响 LD 的丰度。虽然只有一项研究报告了所有这些功能,但其他研究的压倒性和补充证据表明,SQSTM1 通过标记、运动、聚集/聚类和隔离 LDs 来发挥脂噬作用,这在哺乳动物细胞中是一种相当普遍的现象。由于应激条件下 LD 相关蛋白的泛素化被认为是另一种常见现象,一些其他的泛素结合自噬受体,如 NBR1 和 OPTN,可能很快就会与 SQSTM1 一起被列入非排他性脂噬受体的名单中。: LD: 脂质滴; LIR: LC3 相互作用区域; PAT: 脂滴蛋白、ADRP 和 TIP47 结构域; SAR: 选择性自噬受体。